What is the difference between mitosis and meiosis?

The main difference is that meiosis halves the number of chromosomes (2n-->n) whereas mitosis does not. (2n-->2n) Mitosis is simply the division of the nucleus, creating to genetically identical daughter cells. Chromosomes are seperated at the centromere during Anaphase, so that each new cell contains 46 single chromosomes (strictly speaking chromatids). These are replicated during Interphase, resulting in two cells with the full number of chromosomes identical to the mother cell. Meiosis on the other hand creates haploid gametes (sex cells). The main difference is, that not individual chromosomes (so sister chromatids) are seperated, but pairs of homologous chromosomes. This results in two cells with 23 chromosomes (n). After the first division of meiosis, there is no replication and the two cells divide again immediately (division II is just like mitosis). This results in four haploid (n) cells with half the number of chromosomes from the mother cell. These fuse during fertilisation to form a diploid zygote.